Re: [PATCH 3/3] s390x: protvirt: Add new VCPU reset functions

[David Hildenbrand <david@redhat.com>]

On 29.11.19 15:34, Janosch Frank wrote:
> On 11/29/19 3:24 PM, David Hildenbrand wrote:
>> On 29.11.19 15:20, Janosch Frank wrote:
>>> CPU resets for protected guests need to be done via Ultravisor
>>> calls. Hence we need a way to issue these calls for each reset.
>>>
>>> As we formerly had only one reset function and it was called for
>>> initial, as well as for the clear reset, we now need a new interface.
>>>
>>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>>> ---
>>>  target/s390x/cpu.c       | 14 ++++++++++++--
>>>  target/s390x/kvm-stub.c  | 10 +++++++++-
>>>  target/s390x/kvm.c       | 38 ++++++++++++++++++++++++++++++++------
>>>  target/s390x/kvm_s390x.h |  4 +++-
>>>  4 files changed, 56 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
>>> index 829ce6ad54..906285888e 100644
>>> --- a/target/s390x/cpu.c
>>> +++ b/target/s390x/cpu.c
>>> @@ -139,8 +139,18 @@ static void s390_cpu_reset(CPUState *s, cpu_reset_type type)
>>>      }
>>>  
>>>      /* Reset state inside the kernel that we cannot access yet from QEMU. */
>>> -    if (kvm_enabled() && type != S390_CPU_RESET_NORMAL) {
>>> -        kvm_s390_reset_vcpu(cpu);
>>> +    if (kvm_enabled()) {
>>> +        switch (type) {
>>> +        case S390_CPU_RESET_CLEAR:
>>> +            kvm_s390_reset_vcpu_clear(cpu);
>>> +            break;
>>> +        case S390_CPU_RESET_INITIAL:
>>> +            kvm_s390_reset_vcpu_initial(cpu);
>>> +            break;
>>> +        case S390_CPU_RESET_NORMAL:
>>> +            kvm_s390_reset_vcpu_normal(cpu);
>>> +            break;
>>> +        }
>>>      }
>>>  }
>>>  
>>> diff --git a/target/s390x/kvm-stub.c b/target/s390x/kvm-stub.c
>>> index 5152e2bdf1..c4cd497f85 100644
>>> --- a/target/s390x/kvm-stub.c
>>> +++ b/target/s390x/kvm-stub.c
>>> @@ -83,7 +83,15 @@ void kvm_s390_cmma_reset(void)
>>>  {
>>>  }
>>>  
>>> -void kvm_s390_reset_vcpu(S390CPU *cpu)
>>> +void kvm_s390_reset_vcpu_initial(S390CPU *cpu)
>>> +{
>>> +}
>>> +
>>> +void kvm_s390_reset_vcpu_clear(S390CPU *cpu)
>>> +{
>>> +}
>>> +
>>> +void kvm_s390_reset_vcpu_normal(S390CPU *cpu)
>>>  {
>>>  }
>>>  
>>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
>>> index ad6e38c876..502fc71664 100644
>>> --- a/target/s390x/kvm.c
>>> +++ b/target/s390x/kvm.c
>>> @@ -151,6 +151,7 @@ static int cap_s390_irq;
>>>  static int cap_ri;
>>>  static int cap_gs;
>>>  static int cap_hpage_1m;
>>> +static int cap_vcpu_resets;
>>>  
>>>  static int active_cmma;
>>>  
>>> @@ -342,6 +343,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>>>      cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
>>>      cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
>>>      cap_s390_irq = kvm_check_extension(s, KVM_CAP_S390_INJECT_IRQ);
>>> +    cap_vcpu_resets = kvm_check_extension(s, KVM_CAP_S390_VCPU_RESETS);
>>>  
>>>      if (!kvm_check_extension(s, KVM_CAP_S390_GMAP)
>>>          || !kvm_check_extension(s, KVM_CAP_S390_COW)) {
>>> @@ -403,20 +405,44 @@ int kvm_arch_destroy_vcpu(CPUState *cs)
>>>      return 0;
>>>  }
>>>  
>>> -void kvm_s390_reset_vcpu(S390CPU *cpu)
>>> +static void kvm_s390_reset_vcpu(S390CPU *cpu, unsigned long type)
>>>  {
>>>      CPUState *cs = CPU(cpu);
>>>  
>>> -    /* The initial reset call is needed here to reset in-kernel
>>> -     * vcpu data that we can't access directly from QEMU
>>> -     * (i.e. with older kernels which don't support sync_regs/ONE_REG).
>>> -     * Before this ioctl cpu_synchronize_state() is called in common kvm
>>> -     * code (kvm-all) */
>>> +    /*
>>> +     * The reset call is needed here to reset in-kernel vcpu data that
>>> +     * we can't access directly from QEMU (i.e. with older kernels
>>> +     * which don't support sync_regs/ONE_REG).  Before this ioctl
>>> +     * cpu_synchronize_state() is called in common kvm code
>>> +     * (kvm-all).
>>> +     */
>>> +    if (cap_vcpu_resets) {
>>> +        if (kvm_vcpu_ioctl(cs, KVM_S390_VCPU_RESET, type)) {
>>> +            error_report("CPU reset type %ld failed on CPU %i",
>>> +                         type, cs->cpu_index);
>>> +        }
>>> +        return;
>>> +    }
>>>      if (kvm_vcpu_ioctl(cs, KVM_S390_INITIAL_RESET, NULL)) {
>>>          error_report("Initial CPU reset failed on CPU %i", cs->cpu_index);
>>>      }
>>>  }
>>
>> I think I commented this already: The issue is that without
>> cap_vcpu_requests, you would no do a KVM_S390_INITIAL_RESET for type ==
>> S390_CPU_RESET_NORMAL. You have to fence that.
> 
> I did fix that, but not on this branch -_-

You can avoid that completely once you switch to two new separate ioctls ;)


-- 
Thanks,

David / dhildenb